Method and device for magnetic domain refinement of oriented electrical steel plate

ABSTRACT

By optimizing equipment and processing, magnetic domain miniaturization efficiency can be increased, workability can be improved, and processing ability can be increased through same. Provided is a method for miniaturizing the magnetic domains of a directional electric steel plate, the method comprising: a steel plate supporting roll position adjusting step of controlling the vertical direction position of a steel plate while supporting the steel plate progressing along a production line; and a laser emitting step of melting the steel plate by emitting a laser beam to form grooves on the surface of the steel plate, wherein the laser emitting step includes an angle changing step of changing an emitting line angle of the laser beam with respect to a width direction of the steel plate while an optical system emitting the laser beam onto the steel plate is rotated with respect to the steel plate, and a focal distance maintaining step of changing a tilt of the steel plate supporting roll which supports the steel plate according to a change in focal distance of the laser beam in the width direction of the steel plate.

CROSS REFERENCE

This patent application is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/KR2016/015160, filed on Dec. 23, 2016, which claims the benefit of Korean Patent Application No. 10-2016-0008389, filed on Jan. 22, 2016, the entire contents of each are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a method and a device for miniaturizing magnetic domains of a directional electric steel plate which permanently miniaturizes magnetic domains of a steel plate by emitting a laser to the directional electric steel plate.

BACKGROUND ART

For example, a directional electric steel plate with magnetic characteristics such as low iron loss and high magnetic flux density is required in order to reduce power loss and improve efficiency of electric devices such as a transformer.

There is disclosed a technique of miniaturizing magnetic domains in a vertical direction to a rolling direction by a mechanical method or emitting a laser beam to a surface of the steel plate so as to reduce the iron loss of the directional electric steel plate.

The method for miniaturizing the magnetic domains may be broadly divided into temporal magnetic domain miniaturization and permanent magnetic domain miniaturization depending on whether or not an effect of improving magnetic domain miniaturization after the stress removing and annealing is maintained.

The temporal magnetic domain miniaturization method has a disadvantage of losing the magnetic domain miniaturization effect after the stress removing and annealing. In the temporal magnetic domain miniaturization method, the magnetic domains are miniaturized by forming a local compression stress portion on the surface of the steel plate. However, such a method causes damage to an insulating coating layer on the surface of the steel plate and thus, recoating is required, and there is a disadvantage that the manufacturing cost is high because the magnetic domain miniaturization is performed in an intermediate process rather than a final product

The permanent magnetic domain miniaturization method may maintain an effect of improving the iron loss even after heat treatment. For the permanent magnetic domain miniaturization, techniques using an etching method, a roll method, and a laser method have been mainly used. In the case of the etching method, it is difficult to control groove formation depth and width, and it is difficult to guarantee the iron loss property of the final product, and it is disadvantageous in that the etching method is not eco-friendly because an acid solution is used. In the case of the method using the roll, there is a disadvantage that the stability, reliability, and process are complicated for mechanical processing.

In the method for miniaturizing the magnetic domains of the steel plate by using a laser, molten grooves are formed on the surface of the steel plate by emitting a laser beam to the surface of the steel plate while the steel plate is supported and the tension is adjusted, thereby miniaturizing magnetic domains. As described above, in order to miniaturize the magnetic domains using the laser, it is required to improve and optimize the process more effectively so that the iron loss of the electric steel plate is reduced and the magnetic flux density is increased while high-speed processing can be performed.

DISCLOSURE Technical Problem

The present invention has been made in an effort to provide a device and a method for miniaturizing magnetic domains of a directional electric steel plate having advantages of enhancing efficiency of magnetic domain miniaturization and improving workability by optimizing equipments and processes, thereby enhancing processing ability.

The present invention has been also made in an effort to provide a device and a method for miniaturizing magnetic domains of a directional electric steel plate having advantages of preventing a depth deviation of grooves according to a change in focal distance of the laser beam.

The present invention has been also made in an effort to provide a device and a method for miniaturizing magnetic domains of a directional electric steel plate having advantages of enhancing more iron loss improvement efficiency and minimizing reduction of magnetic flux density.

The present invention has been also made in an effort to provide a device and a method for miniaturizing magnetic domains of a directional electric steel plate having advantages of enhancing quality of products by more efficiently removing contaminants such as hill up and spatters formed by laser emitting.

The present invention has been also made in an effort to provide a device and a method for miniaturizing magnetic domains of a directional electric steel plate having advantages of providing an optimal operating environment required for processes.

Technical Solution

An exemplary embodiment of the present invention provides a method for miniaturizing magnetic domains of a directional electric steel plate including: a steel plate supporting roll position adjusting step of controlling the vertical direction position of a steel plate while supporting the steel plate progressing along a production line; a laser emitting step of melting the steel plate by emitting a laser beam to form grooves on the surface of the steel plate,

wherein the laser emitting step includes an angle changing step of changing an emitting line angle of the laser beam with respect to a width direction of the steel plate while an optical system emitting the laser beam onto the steel plate is rotated with respect to the steel plate, and a focal distance maintaining step of changing a tilt of the steel plate supporting roll which supports the steel plate according to a change in focal distance of the laser beam in the width direction of the steel plate.

In the angle changing step, the emitting line angle of the laser beam with respect to the width direction of the steel plate may be changed to a range of ±4°.

The focal distance maintaining step may include a tilt angle calculating step of calculating a tilt of the steel plate supporting roll in accordance with a change in focal distance of the laser beam on the surface of the steel plate due to the rotation of the optical system, and a tilt adjusting step of changing the tilt of the steel plate supporting roll by moving both ends of the steel plate supporting roll up and down according to the value calculated in the tilt angle calculating step, respectively.

The tilt angle calculation step may include an optical system angle calculating step of calculating a rotation angle of the optical system in accordance with the angle of the laser beam emitting line, a tilt calculating step of calculating a tilt angle of the steel plate supporting roll in accordance with the rotation angle of the optical system calculated by the optical system angle calculating step, and a roll controlling step of calculating a stretch driving amount of each of the elevating cylinders disposed at both ends of the steel plate supporting roll in accordance with the tilt value calculated in the tilt calculating step and applying an output signal to each of the elevating cylinders.

In the optical system angle calculating step, the rotation angle of the rotated optical system may be calculated in accordance with the interval of the laser beam and the angle of the emitting line from the moving speed of the steel plate.

In the laser emitting step, with respect to the surface of the steel plate progressing in contact with the surface of the steel plate supporting roll in the form of an arc, by setting as a reference point an emitting position of the laser beam when the emitting direction of the laser beam passes through a central axis of the steel plate supporting roll, the laser beam may be emitted to a position separated at a angle along an outer peripheral surface from the center of the steel plate supporting roll at the reference point.

In the laser emitting step, the laser beam may be emitted in a range of 3 to 7° separated from the center of the steel plate supporting roll along the outer peripheral surface thereof with respect to the reference point.

The method may further include a setting maintaining step of setting and maintaining an internal operating environment of the laser room in which the laser emitting is performed.

The method may further include a tension control step of applying tension to the steel plate so as to keep the steel plate in a flatly unfolded state.

The method may further include a warp controlling step of moving the steel plate without biasing the left and right along the center of the production line.

The setting maintaining step may include steps of isolating the inside of the laser room from the outside to block the inflow of external contaminants, and controlling an internal temperature, pressure, and humidity of the laser room.

The method may further include a post-treatment step of removing hill up and spatters formed on the surface of the steel plate through the laser emitting step.

The post-treatment step may include a brush step of removing the hill up and spatters attached on the surface of the steel plate by a brush roll.

The post-treatment step may further include a cleaning step of removing the hill up and spatters remaining on the surface of the steel plate by electrolytically reacting the steel plate with an alkali solution, and a filtering step of filtering foreign substances removed from the steel plate in the cleaning step and contained in the alkaline solution from the alkaline solution.

The warp control step may include a warp amount measuring step of measuring a warp amount when a width center position of the steel plate deviates from the center of the production line, and a warp amount controlling step of controlling a warp amount of the steel plate by rotating and moving a shaft of the steering roll according to the warp amount of the steel plate measured in the warp amount measuring step to adjust the moving direction of the steel plate.

In the warp amount controlling step, the warp amount of the steel plate may be controlled within ±1 mm.

The tension controlling step may include a steel plate tension applying step of applying tension to the steel plate by the tension bridle roll, a steel plate tension measuring step for measuring the tension of the steel plate subjected to the steel plate tension applying step, and a steel plate tension controlling step of controlling the tension of the steel plate by adjusting a speed of the tension bridle roll according to the tension of the steel plate measured in the steel plate tension measuring step.

The steel plate supporting roll position adjusting step may include a steel plate supporting step of supporting the steel plate positioned in the laser emitting step by the steel plate supporting roll, a brightness measuring step of measuring brightness of a flame occurring when the laser is emitted to the steel plate in the laser emitting step, and a steel plate supporting roll position control step of controlling the steel plate to be located within a depth of focus of the laser by adjusting the position of the steel plate supporting roll by the steel plate supporting roll position control system according to the brightness of the flame measured in the brightness measuring step.

The laser emitting step may include a laser emitting and energy transmission step of forming grooves having an upper width, a lower width and a depth within 70 μm, within 10 μm, and 3 to 30 μm, respectively, by emitting the laser beam emitted from the laser oscillator to the surface of the steel plate by the optical system, and simultaneously transmitting to the steel plate the laser energy density within the range of 1.0 to 5.0 J/mm² required for the melting of the steel plate so that a re-coagulation part remaining on the inner wall surface of the groove of the melting part is generated during the laser emitting

The laser emitting step may include may include a laser beam oscillation control step of controlling the laser oscillator oscillating the laser beam to turn on under normal operation conditions by a laser oscillator controller and controlling the laser oscillator to turn off when the steel plate warp amount is 15 mm or more.

In the laser emitting step, the laser oscillator may oscillate a single mode continuous wave laser beam.

In the laser emitting step, the optical system may adjust an interval of the laser emitting line to 2 to 30 mm in the rolling direction by controlling a laser scanning speed.

The laser emitting step may further include a dust collecting step of sucking and removing fumes and molten iron generated during the laser beam emitting. The dust collecting step may include a spraying step of removing the molten iron remaining in the grooves by spraying compressed dry air into the grooves of the steel plate.

The laser emitting step may further include a shielding step of shielding scattering light and heat of the laser beam from flowing into the optical system of the laser emitting equipment.

Another exemplary embodiment of the present invention provides a device for miniaturizing magnetic domains of a directional electric steel plate including: a steel plate supporting roll position adjusting equipment of controlling a vertical direction position of the steel plate while supporting the steel plate moving along a production line; and a laser emitting equipment of melting the steel plate by emitting a laser beam to form grooves on the surface of the steel plate, wherein the laser emitting equipment has a structure of changing the angle of the emitting line of the laser beam with respect to the width direction of the steel plate by rotating the optical system with respect to the steel plate because the optical system emitting the laser beam to the steel plate is rotatable by a driving unit, and further includes a focal distance maintaining unit which changes the tilt of the steel plate supporting roll supporting the steel plate according to a change in focal distance of the laser beam along the width direction of the steel plate.

The focal distance maintaining unit may include a controller for calculating the tilt of the steel plate supporting roll in accordance with the change in focal distance of the laser beam on the surface of the steel plate due to the rotation of the optical system and controlling the tilt of the steel plate supporting roll, and elevating cylinders and which are provided at both ends of the steel plate supporting roll, respectively, and driven in accordance with a signal of the controller to lift and lower vertically the both ends of the steel plate supporting roll to change the tilt.

The controller may include an optical system angle calculating unit for calculating a rotation angle of the optical system in accordance with the angle of the laser beam emitting line, a tilt angle calculating unit for calculating a tilt angle of the steel plate supporting roll in accordance with the rotation angle of the optical system calculated by the optical system angle calculating unit, and a roll controller for calculating a stretch driving amount of each of the elevating cylinders and disposed at the both ends of the steel plate supporting roll in accordance with the tilt value calculated by the tilt calculating unit and applying an output signal to each of the elevating cylinders.

The controller may further include an input unit for inputting a laser beam emitting interval, a steel plate moving speed, and an angle of the emitting line.

The optical system angle calculating unit may calculate a rotation angle of the optical system rotated in accordance with the angle of the emitting line from the emitting interval of the laser beam and the moving speed of the steel plate.

The laser emitting equipment may emit the laser beam to a position separated at a angle along an outer peripheral surface from the center of the steel plate supporting roll at a reference point, by setting as the reference point an emitting position of the laser beam when the emitting direction of the laser beam passes through a central axis of the steel plate supporting roll, with respect to the surface of the steel plate progressing in contact with the surface of the steel plate supporting roll in the form of an arc.

The laser emitting equipment may emit the laser beam in a range of 3 to 7° separated from the center of the steel plate supporting roll along the outer peripheral surface thereof with respect to the reference point.

The device may further include a laser room of accommodating the steel plate supporting roll position adjusting equipment and the laser emitting equipment separately from the outside and providing an operating environment for emitting the laser.

The device may further include a tension control equipment for applying tension to the steel plate so as to keep the steel plate in a flatly unfolded state.

The device may further include a warp control equipment for moving the steel plate along the center of the production line without biasing the left and the right.

The laser room may accommodate the laser emitting equipment and the steel plate supporting roll position adjusting equipment to form a internal space to separate the equipments from the outside and have an inlet and an outlet formed at both sides in a progressing direction of the steel plate, and may include a positive pressure device for raising the internal pressure of the laser room therein, an optical system lower frame separating an upper space in which the optical system of the laser emitting equipment is positioned from a lower space through which the steel plate passes, and a constant temperature and humidity controller for controlling the internal temperature and humidity of the laser room.

The device may further include a post-treatment equipment for removing hill up and spatters formed on the surface of the steel plate.

The post-treatment equipment may include brush rolls and disposed at the rear end of the laser room to remove the hill-up and spatters of the steel plate surface.

The post-treatment equipment may further include a cleaning unit disposed at the rear end of the brush rolls to further remove the hill up and spatters remaining on the surface of the steel plate by electrolytically reacting the steel plate with an alkali solution, and a filtering unit connected to the cleaning unit to filter the foreign substances contained in the alkaline solution of the cleaning unit.

The warp control equipment may include steering rolls for shifting a moving direction of the steel plate, a warp measurement sensor for measuring a degree (warp amount) when a width center position of the steel plate deviates from the center of the production line, and a steel plate center position control system for controlling a moving direction of the steel plate by rotating and moving shafts of the steering rolls according to the output value of the warp measurement sensor.

The tension control equipment may include tension bridle rolls for guiding movement of the steel plate while applying a tension to the steel plate, a steel plate tension measuring sensor for measuring the tension of the steel plate passing through the tension bridle roll, and a steel plate tension control system for adjusting speeds of the tension bridle rolls according to the tension of the steel plate measured by the steel plate tension measuring sensor.

The steel plate supporting roll position adjusting equipment may include a steel plate supporting roll for supporting the steel plate to the position of the laser emitting equipment, a brightness measurement sensor for measuring brightness of flame occurring when the laser is emitted to the steel plate in the laser emitting equipment, and a steel plate supporting roll position control system for controlling the position of the steel plate supporting roll in accordance with the brightness of the flame measured by the brightness measurement sensor.

The laser emitting equipment may include a laser oscillator for oscillating a continuous wave laser beam, and an optical system of forming grooves having an upper width, a lower width and a depth within 70 μm, within 10 μm, and 3 to 30 μm, respectively, by emitting the laser beam oscillated from the laser oscillator onto the steel plate surface, and simultaneously transmitting to the steel plate the laser energy density within the range of 1.0 to 5.0 J/mm² required for the melting of the steel plate so that a re-coagulation part remaining on the inner wall surface of the groove of the melting part is generated during the laser emitting

The laser emitting equipment may further include a laser oscillator controller of controlling the laser oscillator to turn on under normal operation conditions by a laser oscillator controller and controlling the laser oscillator to turn off when the steel plate warp amount is 15 mm or more.

The laser oscillator may oscillate a single mode continuous wave laser beam.

The optical system may adjust an interval of the laser emitting line to 2 to 30 mm in the rolling direction by controlling a laser scanning speed.

The laser emitting equipment may further include a shielding unit of shielding laser scattering light and heat from flowing into the optical system.

The laser emitting equipment may further include a molten iron removing equipment for removing fumes and spatters generated by emitting the laser beam to the steel plate.

The molten iron removing equipment may include an air knife for spraying compressed dry air into the grooves of the steel plate to remove molten iron remaining in the grooves, and dust collecting hoods for sucking and removing the fumes and the molten iron.

Advantageous Effects

According to the exemplary embodiment of the present invention, it is possible to secure iron loss improvement rates before and after heat treatment of an electrical steel plate at 5% or more and 10% or more, respectively, by stably performing a magnetic domain miniaturizing process by a laser while the steel plate is moved at a high speed of 2 m/sec or more.

Further, it is possible to reduce a depth deviation of grooves in the entire emitting line formed on the steel plate by the laser beam and form grooves with a uniform depth by controlling a tilt of the steel plate supporting roll according to a change in focal distance of the laser beam. As a result, it is possible to enhance quality of the grooves.

Further, it is possible to prevent a back reflection phenomenon caused by the reflection of the laser beam, thereby preventing damage to the equipments.

Further, it is possible to enhance the magnetic domain miniaturizing efficiency and improve the workability, thereby increasing the magnetic domain miniaturizing ability.

Further, it is possible to further improve the iron loss improvement efficiency and minimize deterioration of the magnetic flux density.

Further, it is possible to enhance the quality of products by more efficiently removing contaminants such as hill up and spatters formed by laser emitting.

Further, it is possible to mass-produce high-quality products by providing an optimal operating environment required for processes.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating a configuration of a device for miniaturizing magnetic domains of a directional electric steel plate according to the present exemplary embodiment.

FIG. 2 is a schematic diagram illustrating a steel plate subjected to magnetic domain miniaturization according to the present exemplary embodiment.

FIG. 3 is a schematic diagram illustrating a change in focal distance of a laser beam according to rotation of an optical system for the steel plate according to the present exemplary embodiment.

FIG. 4 is a schematic diagram illustrating a structure of a focal distance maintaining unit for adjusting a tilt of a steel plate supporting roll according to the present exemplary embodiment.

FIG. 5 is a graph illustrating a comparison of a groove depth of a emitting line formed on the steel plate according to the present exemplary embodiment with the related art.

MODE FOR INVENTION

The terms used below is for the purpose of describing specific exemplary embodiments only and are not intended to be limiting of the present invention. The singular forms used herein include plural forms as well, if the phrases do not clearly have the opposite meaning. “including” used in the specification means that a specific feature, region, integer, step, operation, element and/or component is embodied and other specific features, regions, integers, steps, operations, elements, components, and/or groups are not excluded.

Hereinafter, exemplary embodiments of the present invention will be described so as to be easily implemented by those skilled in the art, with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Therefore, the present invention can be implemented in various different forms, and is not limited to the exemplary embodiments described herein.

In the following description, as the present exemplary embodiment, a equipment for permanent magnetic domain miniaturization of a directional electric steel plate used in a transformer iron core material and the like will be described.

FIG. 1 schematically illustrates a device for miniaturizing magnetic domains of a directional electric steel plate according to the present exemplary embodiment and FIG. 2 illustrates a steel plate subjected to magnetic domain miniaturization according to the present exemplary embodiment. In the following description, a rolling direction or a steel plate moving direction means an x-axis direction in FIG. 2, a width direction means a y-axis direction in FIG. 2 as a direction perpendicular to the rolling direction, and a width means a length of a steel plate for the y-axis direction. In FIG. 2, reference numeral 31 indicates a emitting line formed continuously on the surface of a steel plate 1 with a groove shape dented by a laser beam.

Referring to FIG. 1, the device for miniaturizing the magnetic domains of the directional electric steel plate according to the present exemplary embodiment is stably subjected to permanent magnetic domain miniaturization even if the miniaturization progresses at a high speed of 2 m/s or more.

The device for miniaturizing the magnetic domains of the present exemplary embodiment includes a steel plate supporting roll position adjusting equipment for controlling a vertical direction position of the steel plate while supporting the steel plate 1 moving along a production line, a laser emitting equipment for melting the steel plate by emitting a laser beam to form a groove on the surface of the steel plate, and a laser room 20 for accommodating the steel plate supporting roll position adjusting equipment and the laser emitting equipment separately from the outside and providing an operational environment for laser emitting.

In addition, the device for miniaturizing the magnetic domains may further include a tension control equipment for applying the tension to the steel plate so as to allow the steel plate to be maintained in a flat state without sagging.

In addition, the device for miniaturizing the magnetic domains may further include a warp control equipment for allowing the steel plate to move left and right along the center of the production line without tilting.

In addition, the device for miniaturizing the magnetic domains may further include a post-treatment equipment for removing hill-up and spatter formed on the surface of the steel plate in accordance with the laser beam emitting.

The hill-up refers to a portion where molten iron is accumulated on both sides of the groove portion at a predetermined height or more when the groove is formed by emitting the laser beam to the surface of the steel plate. The spatter refers to molten iron generated during laser beam emitting and solidified on the surface of the steel plate.

In addition, the device further includes a focal distance maintaining unit for constantly maintaining a focal distance of the laser beam on the surface of the steel plate by changing the tilt of the steel plate supporting roll supporting the steel plate in accordance with the change in focal distance of the laser beam along a width direction of the steel plate. A detailed structure of the focal distance maintaining unit will be described below in more detail.

The warp control equipment may include steering rolls 2A and 2B for shifting a moving direction of the steel plate 1, a warp measurement sensor 4 for measuring a degree (warp amount) when a width center position of the steel plate 1 deviates from the center of the production line, and a steel plate center position control system 3 for controlling a moving direction of the steel plate 1 by rotating and moving shafts of the steering rolls 2A and 2B by calculating a detection signal of the warp measurement sensor 4.

The warp measurement sensor 4 is disposed at the rear end of the steering roll 2B to detect in real time the actual warp amount of the steel plate passing through the steering roll.

It is possible to form the grooves on the surface of the steel plate over the entire width of the steel plate by straightly moving the steel plate along the center of the production line by the warp control equipment.

In the warp control equipment, the warp amount of the steel plate is measured by the warp measurement sensor 4 in the process before the grooves are formed on the surface of the steel plate by laser emitting. The values measured by the warp measurement sensor 4 are output to the steel plate center position control system, and the steel plate center position control system calculates the output values of the warp measurement sensor and rotates and rotates the axes of the steering rolls 2A, 2B according to the calculated warp degree. As described above, the steering rolls 2A and 2B are rotated and moved, so that the moving direction of the steel plate wound on the steering roll is adjusted. Thus, the warp amount of the steel plate is controlled, and the warp amount of the steel plate 1 may be controlled within ±1 mm.

The tension control equipment may include tension bridle rolls (TBRs) 5A and 5B for guiding movement of the steel plate 1 while applying a predetermined tension to the steel plate 1, a steel plate tension measuring sensor 7 for measuring the tension of the steel plate 1 passing through the tension bridle roll, and a steel plate tension control system 6 for adjusting speeds of the tension bridle rolls 5A and 5B according to the tension of the steel plate measured by the steel plate tension measuring sensor 7.

The steel plate tension measuring sensor 7 is disposed at the rear end of the tension bridle roll 5B and measures the actual tension of the steel plate subjected to the tension via the tension bridle roll 5B in real time

In the present exemplary embodiment, the tension of the steel plate may be set so as to prevent the breakage of the steel plate from occurring due to excessively tension while making the shape of the surface of the steel plate flat at the laser emitting position of the laser emitting equipment.

In order to operate the tension control equipment by the steel plate tension within a predetermined range, the tension control equipment adjusts the speeds of the tension bridle rolls (TBR) 5A and 5B by the steel plate tension control system 6 according to the tension of the steel plate measured by the steel plate tension measurement sensor 7. Thus, the tension control equipment controls a tension error of the steel plate 1 to be within the predetermined range to apply the tension to the steel plate.

The steel plate passing through the tension control equipment flows into the laser room 20, and is subjected to the magnetic domain miniaturization through the steel plate supporting roll position adjusting equipment and the laser emitting equipment and then discharged to the outside of the laser room 20. The laser room will be described below again.

In the present exemplary embodiment, a steel plate supporting roll 9 is disposed directly below the laser emitting equipment in the laser room 20, and deflector rolls 8A and 8B are provided on both sides with the steel plate supporting roll interposed therebeween.

The moving direction of the steel plate 1 is shifted toward the steel plate supporting roll 9 by the deflector rolls 8A and 8B. While the steel plate 1 passes through the deflector roll 8A, the moving direction is shifted toward the steel plate supporting roll 9 so that the steel plate 1 is in contact with the steel plate supporting roll 9, and then the moving direction is shifted toward the deflector roll 8B so that the steel plate 1 moves through the deflector roll 8B.

The steel plate 1 is wound in an arc form along the steel plate supporting roll 9 by the deflector roll and passes while being in surface contact with the steel plate supporting roll. In order to minimize the variation of the focal distance of the laser beam due to the vibration and waving of the steel plate during the emitting of the laser beam, the steel plate needs to pass while being sufficiently in surface contact with the steel plate supporting roll, and in this state, the laser beam needs to be emitted to the steel plate progressing along the steel plate supporting roll. In the present exemplary embodiment, as the steel plate is in surface contact with the steel plate supporting roll as described above, it is possible to accurately emit the laser beam to the steel plate.

The steel plate supporting roll position adjusting equipment may include a steel plate supporting roll 9 for supporting the steel plate 1 to the laser emitting position of the laser emitting equipment, a brightness measurement sensor 10 for measuring brightness of flame occurring when the laser is emitted to the steel plate in the laser emitting equipment, and a steel plate supporting roll (SPR) position control system 12 for controlling the position of the steel plate supporting roll 9 in accordance with the brightness of the flame measured by the brightness measurement sensor 10.

The steel plate supporting roll position adjusting equipment is configured to support the steel plate 1 to the position of the laser emitting unit by the steel plate supporting roll 9 and entirely vertically adjust the position of the steel plate 1 to be disposed in a depth of focus having high laser steel plate emitting efficiency so that the brightness of the flame generated when the steel plate is emitted with the laser becomes the best. Further, the brightness of the flame generated when the steel plate is emitted with the laser is measured by using the brightness measurement sensor 10.

In the present exemplary embodiment, the steel plate supporting roll position adjusting equipment may further include a distance measurement sensor 11 for measuring an actual distance from the optical system of the laser emitting equipment to the surface of the steel plate. The steel plate supporting roll position control system 12 calculates the brightness of the flame detected from the brightness measurement sensor 10 and the distance between the optical system and the surface of the steel plate actually measured from the distance measuring sensor 11 to more precisely control the position of the steel plate supporting roll 9.

The steel plate control equipment, the tension control equipment, and the steel plate supporting roll position adjusting equipment serve to make steel plate conditions at the laser emitting position so that the laser grooves may be formed precisely on the steel plate by the laser emitting equipment. In the steel plate at the laser emitting position, the center position of the steel plate needs to be positioned at the center position of the production line and the distance from the optical system needs to be maintained at the set value.

The laser emitting equipment may include a laser oscillator controller 13, a laser oscillator 14 for oscillating a continuous wave laser beam 16, and an optical system 15.

If the warp amount of the steel plate is excessive, the steel plate deviates from the laser emitting position, and the steel plate supporting roll 9 is emitted with the laser to be damaged. As a result, in order to prevent the damage to the steel plate supporting roll, the laser oscillator controller 13 turns on the laser oscillator under normal operation conditions and controls the laser oscillator to turn off when the steel plate warp amount is 15 mm or more.

The laser oscillator 14 may oscillate a single mode continuous wave laser beam to transmit the oscillated laser beam to the optical system 15. The optical system 15 emits the transmitted laser beam 16 to the surface of the steel plate.

The laser oscillator 14 and the optical system 15 may emit the laser beam to the surface of the steel plate to form grooves with an upper width, a lower width and a depth of 70 μm or less, 10 μm or less, and 3 to 30 μm, respectively, and transmit laser energy density to the steel plate in the range of 1.0 to 5.0 J/mm² required for melting the steel plate so that a re-coagulation portion is generated to remain on the inner wall surface of the groove in the melting portion during laser emitting.

The optical system 15 has a function of controlling a laser scanning speed to adjust an interval of the laser emitting line (31 in FIG. 2) to 2 to 30 mm in the rolling direction. Therefore, the influence of a heat affected zone (HAZ) by the laser beam may be minimized, thereby improving the iron loss of the steel plate.

Further, in the present exemplary embodiment, the laser emitting equipment controls the emitting position of the laser beam to the steel plate 1 to have a structure for preventing a back reflection phenomenon in which the laser beam emitted to the steel plate is reflected from the steel plate to enter the optical system or the laser oscillator.

To this end, as illustrated in FIG. 3, the laser emitting equipment may be a structure in which the laser beam is emitted to a position separated at an angle (hereinafter, referred to as a separation angle R for convenience of description) along an outer peripheral surface at the center of the steel plate supporting roll 9 from a reference point P by setting a laser beam emitting position when the emitting direction of the laser beam emitted from the optical system 15 passes through the central axis of the steel plate supporting roll 9, with respect to the surface of the steel plate which progresses in contact with the surface of the steel plate supporting roll 9 in an arc form.

The reference point P is a point in which the steel plate meets a line passing through the central axis of the steel plate supporting roll 9. When the emitting direction of the laser beam passes through the central axis of the steel plate supporting roll 9, the focal point of the laser beam is adjusted to the reference point P. In this case, as the emitting direction of the laser beam is orthogonal to a tangential line of the steel plate supporting roll 9 at the reference point P, a back reflection phenomenon occurs, in which the laser beam reflected onto the steel plate enters the optical system and the laser oscillator as it is to damage the steel plate.

The laser emitting equipment according to the present exemplary embodiment emits the laser beam to the position separated by the separation angle R at the reference point P and thus the laser beam reflected back from the steel plate is not incident to the optical system. Therefore, it is possible to prevent the back reflection phenomenon and to maintain the quality of the groove shape formed by the laser beam.

In the present exemplary embodiment, the separation angle R may be set in a range of 3 to 7° along the outer peripheral surface at the center of the steel plate supporting roll 9 with respect to the reference point P.

When the separation angle R, which is the position at which the laser beam is emitted, is smaller than 3°, a part of the laser beam reflected back from the steel plate may be introduced into the optical system or the laser oscillator. If the separation angle R exceeds 7°, the grooves are not properly formed by the laser beam and a formation defect of the groove may occur.

As such, the laser emitting equipment according to the present exemplary embodiment emits the laser beam to the steel plate at a position separated from the reference point P by a predetermined angle, thereby preventing the back reflection phenomenon and stably maintaining the quality of the groove shape formed by the laser beam.

As illustrated in FIG. 3, the laser emitting equipment may be a structure for changing the angle of the emitting line of the laser beam emitted on the surface of the steel plate with respect to the width direction of the steel plate.

In the present exemplary embodiment, the laser emitting equipment may change the angle of the emitting line of the laser beam to a range of ±4° with respect to the width direction of the steel plate.

To this end, the laser emitting equipment may be a structure of changing the angle of the emitting line of the laser beam to a range of ±4° with respect to the width direction of the steel plate because the optical system 15 for emitting the laser beam to the steel plate is rotatable by a driving unit (not illustrated). As such, the angle of the emitting line of the laser beam is changed by the optical system, and thus, the emitting line 31 by the laser beam is inclined in the range of ±4° in a direction perpendicular to the rolling direction of the steel plate. Therefore, it is possible to minimize the decrease in the magnetic flux density due to the groove formation by the laser.

As such, the optical system 15 is rotated at a predetermined angle with respect to the width direction of the steel plate in order to tilt the angle of the emitting line of the laser beam at a predetermined angle with respect to the width direction of the steel plate. While the steel plate progresses in a state in which the steel plate is in contact with the circular steel plate supporting roll in an arc form to form a curved surface, the optical system is rotated in the same manner to be warped in the width direction of the steel plate, and as a result, the emitting direction of the laser beam emitted from the optical system is also warped in the width direction of the steel plate.

FIG. 3 illustrates that since the laser beam of the optical system is warped in the width direction of the steel plate as the optical system rotates at the rotation angle with respect to the width direction of the steel plate as described above, the focal distance is changed. In FIG. 3, reference numeral L mean a line segment passing through the width direction of the steel plate, and reference numeral W means an emitting line of the laser beam emitted onto the surface of the steel plate by the rotated optical system. This emitting line L may be understood as the emitting line 31 of the laser beam when the movement of the steel plate is not considered. Reference numeral A means a rotation angle of the optical system with respect to the width direction of the steel plate.

As illustrated in FIG. 3, when the optical system 15 is rotated at an angle with respect to the width direction of the steel plate, based on a point C where the line segment L passing through the width direction of the steel plate and the emitting line W of the laser beam emitted from the rotated optical system meet each other, the position of the steel plate is relatively high toward the right end, and thus, a distance D between the optical system of the laser emitting equipment and the steel plate is gradually decreased, and the position of the steel plate is relatively low toward the left side which is an opposite end, and thus, a distance E between the optical system and the steel plate is gradually increased. As such, the distance between the optical system 15 and the steel plate 1 varies according to the emitting line W, and the focal distance of the laser beam emitted onto the steel plate in the optical system is changed.

The focal distance maintaining unit of the present exemplary embodiment uniformly maintains the focal distance by correcting the change in focal distance of the laser beam generated while the optical system 15 is rotated in accordance with the emitting line angle.

As such, when the focal distance of the laser beam is changed with respect to the surface of the steel plate, the depth of the groove formed on the steel plate is not uniform, and in the case of deviating from an effective focal distance, there is a serious problem that grooves are not formed on the steel plate.

Therefore, the device of the present exemplary embodiment includes the focal distance maintaining unit to change the tilt of the steel plate supporting roll 9 supporting the steel plate in accordance with the change in focal distance of the laser beam with respect to the width direction of the steel plate according to the emitting line angle, thereby uniformly maintaining the focal distance.

FIG. 4 illustrates a configuration of the focal distance maintaining unit according to the present exemplary embodiment.

As illustrated in FIG. 4, the focal distance maintaining unit may include a controller 45 for calculating the tilt of the steel plate supporting roll 9 in accordance with the change in focal distance of the laser beam on the surface of the steel plate due to the rotation of the optical system and controlling the tilt of the steel plate supporting roll, and elevating cylinders 43 and 44 which are provided at both ends of the steel plate supporting roll 9, respectively, and driven in accordance with a signal of the controller 45 to lift and lower vertically the both ends of the steel plate supporting roll to change the tilt.

The controller 45 includes an optical system angle calculating unit 46 for calculating a rotation angle of the optical system in accordance with the angle of the laser beam emitting line, a tilt angle calculating unit 45 for calculating a tilt angle of the steel plate supporting roll in accordance with the rotation angle of the optical system calculated by the optical system angle calculating unit 46, and a roll controller 48 for calculating a stretch driving amount of each of the elevating cylinders 43 and 44 disposed at the both ends of the steel plate supporting roll in accordance with the tilt value calculated by the tilt calculating unit and applying an output signal to each of the elevating cylinders.

The controller 45 may further include an input unit 49 for inputting a laser beam emitting interval, a steel plate moving speed, and an angle of the emitting line.

The optical system angle calculating unit 46 calculates the rotation angle of the optical system 15 rotated at an appropriate angle in accordance with the emitting line angle. The optical system angle calculating unit 46 may be configured to calculate the rotation angle of the optical system rotated in accordance with the angle of the emitting line by considering the influence of the emitting interval of the laser beam and the moving speed of the steel plate. That is, the optical system angle calculating unit 46 calculates the rotation angle of the optical system from the laser beam emitting interval, the steel plate moving speed, and the set emitting angle.

In the present exemplary embodiment, the optical system angle calculating unit 46 pre-stores Equation 1 for calculating the laser beam emitting angle formed on the steel plate according to the laser beam emitting interval and the emitting width therein and Equation 2 for calculating the rotation angle of the optical system for the given angle of the emitting line. As a result, the optical system angle calculating unit first calculates an emitting angle of the laser beam generated according to the influence of the steel plate movement from the following Equation 1 through each dimension applied from an input unit 49 and calculated a rotation angle A of the actual optical system by reflecting the value to the following Equation 2. Laser beam emitting angle=sin⁻¹(laser beam emitting interval/laser beam emitting width)  Equation 1:

The laser beam emitting angle means an angle formed by tilting the emitting line of the laser beam with respect to the steel plate width direction as the steel plate moves even while the optical system is not rotated. Optical system rotation angle A=Emitting line angle−Laser beam emitting angle  Equation 2:

In Equation 2, the angle of the emitting line is an angle of the emitting line formed by emitting the laser beam onto the steel plate with respect to the width direction of the steel plate. The radiation angle is a value obtained by adding the laser beam emitting angle in consideration of the steel plate movement and the emitting angle of the laser beam according to the rotation of the optical system from the above Equation 1. Thus, the rotation angle A of the optical system may be obtained by subtracting the laser beam emitting angle obtained from the Equation 1 from the set emitting angle.

The tilt calculating unit 47 calculates a tilt B of the steel plate supporting roll in accordance with the rotation angle of the optical system calculated from the optical system angle calculating unit 46.

The tilt calculating unit 47 pre-stores Equation 3 for calculating the tilt of the steel plate supporting roll therein. Thus, the tilt calculating unit 47 calculates a tilt B of the steel plate supporting roll by reflecting an emitting line coordinate value of the laser beam according to the rotation angle of the optical system obtained by the Equation 2 to the following Equation 3. Tilt B of steel plate supporting roll=tan⁻¹(|Z ₂ −Z ₁ |/|X ₂ −X ₁|)  Equation 3—

The Z₂, Z₁, X₂, and X₁ represent coordinate values on the emitting line W of the laser emitted onto the steel plate surface by the rotated optical system, as coordinate values of a xyz coordinate system in FIG. 3.

Through the Equation 3, the tilt calculating unit 47 may calculate a tilted angle of the laser beam on the steel plate according to the rotation angle of the optical system, that is, a tilt to be reflected to the steel plate supporting roll.

The roll controller 48 pre-stores the following Equation 4 for calculating a stretch driving amount of the elevating cylinders 43 and 44 disposed at both ends of the steel plate supporting roll 9 therein. Thus, the roll controller 48 controls the steel plate supporting roll 9 to a required tilt B by controlling each elevating cylinder according to the stretch driving amount of the elevating cylinders 43 and 44 obtained through the following Equation 4. ΔZ _(left) =M×tan B,ΔZ _(right) =−N×tan B  Equation 4—

Here, ΔZ_(left) represents a stretch driving amount for the left elevating cylinder 43 in FIG. 4 and ΔZ_(right) represents a stretch driving amount for the right elevating cylinder 44. In addition, B represents a tilt value of the steel plate supporting roll 9. The minus (−) at the −N means a value at which the stretch driving amount is minus, that is, a value at which the stretch amount is reduced when the elevating cylinder is not elongated but contracted.

Further, M represents a distance to the left elevating cylinder 43 from a point G where a horizontal-axis line H when the steel plate supporting roll 9 is horizontally disposed meets a tilt-axis line K when the steel plate supporting roll 9 is tilted at the tilt B obtained from the tilt calculating unit 47, and N is a distance from the point G to the right elevating cylinder 44.

As such, the roll controller 48 determines the stretch driving amount of each of the elevating cylinders 43 and 44 in accordance with the tilt B of the steel plate supporting roll through Equation 4 and stretches and drives each elevating cylinder according to the value. The elevating cylinders 43 and 44 are driven in accordance with the control signal of the roll controller 48 to adjust the steel plate supporting roll to the set tilt B.

As illustrated in FIG. 4, in accordance with the change of the laser emitting line W with respect to the steel plate in FIG. 3, the tilt B of the steel plate supporting roll is obtained so that the left side ascends and the right side descends, and the right elevating cylinder 44 is driven to be contracted and the left elevating cylinder 43 is driven to be stretched in accordance with the value.

Thus, the steel plate supporting roll 9 is tilted at the set tilt B, and the axial direction is set along the tilt-axis line K. Therefore, in FIG. 4, the position of the steel plate 1 passing through the right side of the steel plate supporting roll 9 based on the point G becomes lower, and the position of the steel plate passing through the left side becomes higher.

The distance between the optical system 15 and the steel plate 1 becomes longer as the position of the steel plate 1 becomes lower at the right side of the point G. Likewise, the distance between the optical system and the steel plate becomes shorter as the position of the steel plate becomes higher from the left side of the point G. As such, the distance between the optical system and the steel plate is adjusted by the tilt B of the steel plate supporting roll, thereby compensating for a change in distance between the steel plate and the optical system due to the rotation of the optical system.

That is, as illustrated in FIG. 3, the distance between the optical system 15 and the steel plate 1 is shortened at the right side of the steel plate by the rotation of the optical system 15, but as illustrated in FIG. 4, the position of the steel plate becomes lower at the right side of the steel plate by giving the tilt B to the steel plate supporting roll 9, thereby compensating for a reduction amount of the distance between the steel plate and the optical system in FIG. 3. Therefore, the focal distance of the laser beam emitted onto the surface of the steel plate in the optical system is constantly maintained along the emitting line. Thus, the emitting line may be formed on the surface of the steel plate while minimizing a deviation in a width direction groove depth despite the rotation of the optical system.

The laser emitting equipment may further include a molten iron removing equipment for removing fumes and spatters generated by emitting the laser beam onto the steel plate.

The molten iron removing equipment may include an air knife 17 for spraying compressed dry air into the grooves of the steel plate to remove molten iron remaining in the grooves, and dust collecting hoods 19A and 19B for sucking and removing the fumes and the molten iron. The fumes generated during the laser emitting through the air knife and the dust collecting hoods are removed to prevent the fumes from flowing into the optical system. The air knife 17 sprays compressed dry air having a predetermined pressure Pa into the groove of the steel plate 1 to remove the molten iron remaining in the groove. The compressed dry air in the air knife 17 preferably has a pressure Pa of 0.2 kg/cm² or more. When the pressure of the compressed dry air is smaller than 0.2 kg/cm², it is impossible to remove the molten iron in the groove and thus, the iron loss improvement effect can not be secured. The fumes and the spatters removed by the air knife are removed by the dust collecting hoods 19A and 19B disposed before and after the laser emitting position.

In addition, the laser emitting equipment may further include a shielding portion 18 for shielding reflected light, scattered light, and radiant heat of the laser beam from flowing into the optical system. The shielding portion 18 shields the reflected light and scattered light flowing into the optical system by reflection and scattering of the laser beam 16 emitted onto the steel plate to prevent the optical system from being thermally deformed by the radiant heat due to the reflected light and scattered light.

The laser room 20 is a room structure having an internal space and accommodates the laser emitting equipment and the steel plate supporting roll 9 position control equipment therein to isolate the equipments from the outside and provide an appropriate operating environment for smooth driving thereof.

An inlet and an outlet of the laser room 20 are formed on the entrance and exit sides of the laser room 20 along the progressing direction of the steel plate. The laser room 20 has an equipment for blocking the inflow of contaminants so that the internal space is not contaminated by external dust or the like. To this end, the laser room 20 has a positive pressure device 23 for raising the internal pressure beyond the outside. The positive pressure device 23 maintains the internal pressure of the laser room 20 relatively higher than the external pressure. Thus, it is possible to prevent foreign substances from flowing into the laser room 20. In addition, air curtains 22A, 22B, 22C, and 22D are provided at the inlet and the outlet of the steel plate. The air curtain sprays air to the inlet and the outlet, which are passages through which the steel plate enters and exits the laser room 20 to form a film, thereby blocking dust and the like from flowing into through the inlet and the outlet. In order to prevent contamination in the laser room 20, a shower booth 21 may be installed on the door, which is an entrance of the laser room 20. The shower booth 21 removes foreign substances adhering to the body of a passenger entering the laser room 20.

The laser room 20 is a space in which the process of miniaturizing the magnetic domains of the steel plate by the laser beam substantially progresses, and it is necessary to minimize a change of the internal environment and maintain a proper environment. The laser room 20 includes an optical system lower frame 24 for separating an upper space, in which the laser oscillator 14 and the optical system 15 of the laser emitting equipment are located, from a lower space through which the steel plate 1 passes, and a constant temperature and humidity controller 25 for controlling the internal temperature and humidity of the laser room 20.

The optical system lower frame 24 can more thoroughly manage an operating environment of the main equipment such as the laser oscillator 14 and the optical system 15. The optical system lower frame 24 is installed in the laser room 20 so as to separate the lower space of the optical system through which the steel plate passes, from the upper space of the optical system where the laser oscillator and the optical system mirrors are located. The upper space of the optical system is also separated from the inside of the laser room 20 by the optical system lower frame 24 to prevent contamination and easily control the temperature and humidity with respect to major equipments such as the laser oscillator and the optical system.

The constant temperature and humidity controller 25 adjusts the temperature and humidity inside the laser room 20 to provide a proper environment. In the present exemplary embodiment, the constant temperature and humidity controller 25 may maintain the internal temperature of the laser room 20 at 20 to 25° C. and maintain the humidity at 50% or less.

As described above, the internal space of the laser room 20 is continuously maintained at a temperature and humidity suitable for the operating environment, and the process of miniaturizing the magnetic domains may be performed on the steel plate in an optimum state. Therefore, a high-quality product may be mass-produced under an optimal operating environment required for the process.

The device for miniaturizing the magnetic domains of the present exemplary embodiment may further include a post-treatment equipment for removing hill-up and spatters formed on the surface of the steel plate.

Since the hill-up and spatters cause deterioration of an insulation property of the product and a space factor, the hill-up and spatters are completely removed through the post-treatment equipment to enhance the quality of the product.

The post-treatment equipment may include brush rolls 26A and 26B disposed at the rear end of the laser room 20 along a steel plate moving direction to remove the hill-up and spatters of the steel plate surface. The brush rolls 26A and 26B are rotated at a high speed by a driving motor, and a rotation speed and an interval with the steel plate are controlled by a current control system that controls a current value of the driving motor generated during operation to a set target value and a brush position control system that controls an interval between the brush roll and the steel plate. The brush roll may be disposed on only one side of the steel plate having grooves formed by the laser beam, or on both sides of the steel plate. The brush rolls 26A and 26B are brought into close contact with the surface of the steel plate and are rotated at a high speed to remove the hill-up and the spatters attached to the surface of the steel plate. As illustrated in FIG. 1, a dust collecting hood 19C for discharging the hill-up and the spatters removed by the brush roll is further provided near the brush rolls 26A and 26B. The dust-collecting hood 19C sucks molten iron such as the hill-up and the spatters which are separated from the steel plate by the brush rolls 26A and 26B, and discharges the molten iron to the outside.

Further, the post-treatment equipment may further include a cleaning unit 29 disposed at the rear end of the brush rolls 26A and 26B to further remove the hill up and spatters remaining on the surface of the steel plate by electrolytically reacting the steel plate with an alkali solution, and a filtering unit 30 connected to the cleaning unit to filter the foreign substances contained in the alkaline solution of the cleaning unit.

The hill up and the spatters of the steel plate are primarily removed via the brush rolls 26A and 26B, and are secondarily removed via the cleaning unit 29. Thus, it is possible to enhance the product quality by more completely removing the hill up and the spatters attached to the surface of the steel plate.

The cleaning unit 29 is filled with an alkali solution therein, and the filtering unit 30 is connected to one side. As the steel plate is processed through the cleaning unit, the hill up and the spatters removed from the steel plate are accumulated in the internal alkali solution, thereby deteriorating the cleaning performance of the steel plate. The filtering unit 30 circulates the alkali solution of the cleaning unit and removes the hill up and the spatters contained in the alkali solution. The filtering unit 30 removes the hill up and the spatters to control the iron content of the alkali solution to 500 ppm or less. As such, it is possible to continuously process the steel plate by preventing deterioration of the cleaning performance of the cleaning unit.

Hereinafter, the process of miniaturizing the magnetic domains of the electrical steel plate according to the present exemplary embodiment will be described below.

The continuously conveyed steel plate is introduced into the laser room through the warp control equipment and the tension control equipment to progress at a velocity of 2 m/sec or more, and subjected to the magnetic domain miniaturization. The steel plate introduced into the laser room is subjected to the permanent magnetic domain miniaturization through the laser emitting equipment and then drawn out to the outside of the laser room. The steel plate drawn out to the outside of the laser room is sent to the post-treatment after the hill up and the spatters remaining on the surface are removed through the post-treatment equipment.

In this process, the laser room in which the laser beam is emitted to the surface of the steel plate is appropriately set and maintained in the internal operating environment so as to provide an optimal environment for the magnetic domain miniaturization.

The laser room isolates the inside from the outside to block the inflow of external contaminants, and controls the internal temperature, pressure and humidity of the laser room according to the operating environment for the magnetic domain miniaturization.

The internal pressure of the laser room is maintained to be higher than that of the outside so as to prevent foreign substances such as external dust from flowing into the laser room. In addition, by forming a film of air on the inlet and the outlet, which are the passages through which the steel plate is moved, it is possible to prevent foreign substances such as dust from flowing into the laser room in the process where the steel plate progresses through the inlet and the outlet.

Further, the constant temperature and humidity controller installed in the laser room maintains the temperature inside the laser room at 20 to 25° C. and maintains the humidity at 50% or less, thereby providing an optimum condition for the magnetic domain miniaturization by laser emitting.

As such, the laser room provides an optimal environment for laser beam emitting, and the steel plate is accurately positioned at the laser emitting position while passing through the warp control equipment, the tension control equipment, and the steel plate supporting roll position adjusting equipment.

First, for the magnetic domain miniaturization, the steel plate is moved straightly without biasing the left and right along the center of the production line by controlling the progressing direction through the warp control equipment.

The warp measurement sensor continuously detects the warp amount of the steel plate, and when the steel plate is warped, the steel plate center position control system rotates and moves the shaft of the steering roll by calculating a signal detected by the warp measurement sensor to move the steel plate to a correct position

Thus, by continuously controlling the steering rolls according to the position of the steel plate, the steel plate may be continuously moved without departing from the center of the production line.

The steel plate is moved through the tension bridle roll for controlling the tension via the steering roll. The tension of the steel plate passing through the tension bridle roll is detected by the tension measurement sensor. The steel plate tension control system calculates a measurement value detected by the tension measurement sensor and controls the speed of the tension bridle roll according to the set tension. Thus, the tension of the steel plate to be moved may be maintained continuously in accordance with the set range.

The steel plate passed through the tensile bridle roll is introduced into the laser room through the inlet of the laser room. The steel plate is shifted inside the laser room by the bridle roll and moved in a state of being in close contact with the steel plate supporting roll located between the two bridle rolls.

The steel plate supporting roll moves the steel plate up and down to position the steel plate in the depth of focus of the laser beam.

When the laser beam is emitted from the laser emitting equipment to the steel plate, the brightness measurement sensor detects the brightness of the flame on the steel plate surface in real time, and the steel plate supporting roll position control system moves the steel plate supporting roll up and down according to the measured value detected by the brightness measuring sensor to allow the steel plate to be positioned within the depth of focus of the laser beam. Thus, the laser beam is effectively emitted onto the surface of the steel plate, to form a high-quality emitting line.

The laser oscillator controller turns on/off the laser oscillator according to the warp degree of the steel plate. The laser oscillator controller is connected to the warp measurement sensor, and determines that the steel plate deviates too much from the steel plate supporting roll when the warp amount of the steel plate measured from the warp measurement sensor is, for example, 15 mm or more to turn off the laser oscillator. Thus, it is possible to prevent the roll from being damaged by emitting the laser beam on to the surface of the steel plate supporting roll via the warped steel plate.

According to a command of the laser oscillator controller, the laser beam generated by the laser oscillator is emitted onto the surface of the steel plate through the optical system. The laser oscillator oscillates a TEM₀₀ continuous wave laser beam to transmit the oscillated laser beam to the optical system.

The optical system changes the direction of the laser beam and emits the laser onto the surface of the steel plate to continuously form a molten groove on the surface of the steel plate, thereby performing the magnetic domain miniaturization.

While the surface of the steel plate is molten by the laser beam emitted to the steel plate through the optical system, the molten groove is formed along the emitting line. In the present exemplary embodiment, grooves having an upper width, a lower width and a depth within 70 μm, within 10 μm, and 3 to 30 μm, respectively, are formed on the surface of the steel plate through the laser beam emitting. Simultaneously, the laser oscillator and the optical system transmit the laser energy density within the range of 1.0 to 5.0 J/mm² required for the melting of the steel plate to the steel plate so that a re-coagulation part remaining on the inner wall surface of the groove of the melting part is generated during the laser emitting.

Further, by emitting the laser beam at a position R separated from the reference point P in the laser beam emitting process through the optical system, the laser beam reflected back from the steel plate is not incident to the optical system. Therefore, the back reflection phenomenon may be prevented, and the incident light path of the laser beam is not interfered by the reflected light, thereby maintaining the quality of the groove shape formed by the laser beam.

The optical system has a function of controlling a laser scanning speed to adjust the interval of the laser emitting lines with respect to the rolling direction. Further, the optical system has a rotation function to change the angle of the laser emitting line. In the present exemplary embodiment, it is possible to adjust the interval of the laser emitting lines by 2 to 30 mm in the rolling direction by the optical system, thereby minimizing the influence of the heat affected zone (HAZ) and improving the iron loss of the steel plate. Further, in the laser beam emitting process, the angle of the emitting line of the laser beam emitted on the surface of the steel plate may be changed through the rotation of the optical system. In the present exemplary embodiment, the optical system may change the angle of the emitting line of the laser beam into the range of ±4° with respect to the width direction of the steel plate. That is, it is possible to form the emitting line 31 of the laser beam so as to be tilted in the range of ±4° with respect to the y-axis direction in FIG. 2. Therefore, the emitting lines formed on the surface of the steel plate may be formed to be tilted in the range of 86 to 94° with respect to the rolling direction. By forming the emitting line in such a manner as to be tilted with respect to the y-axis direction, it is possible to minimize the decrease in the magnetic flux density due to the groove formation by the laser.

In the processing method of the present exemplary embodiment, when the optical system is rotated as described above to change the angle of the emitting line of the laser beam to a predetermined angle with respect to the width direction of the steel plate, it is possible to continuously constantly maintain the focal distance of the laser beam for the steel plate by changing the tilt of the steel plate supporting roll for supporting the steel plate.

In order to maintain the focal distance, first, the tilt of the steel plate supporting roll is calculated in accordance with the change in the focal distance of the laser beam on the surface of the steel plate due to the rotation of the optical system, and the elevating cylinders installed at both ends of the steel plate supporting roll are moved up and down, respectively, according to the calculated tilt of the steel plate supporting roll to change the tilt of the steel plate supporting roll.

While the tilt of the steel plate supporting roll is changed, the distance between the steel plate and the optical system is changed. As a result, a change amount of the focal distance of the laser beam according to the rotation of the optical system is compensated by the tilt of the steel plate supporting roll, so that the distance between the optical system and the steel plate is constantly maintained. Therefore, the focal distance of the laser beam emitted onto the surface of the steel plate in the optical system is constantly maintained along the emitting line, so that the emitting line may be formed while minimizing a depth deviation of the lateral groove on the surface of the steel plate.

FIG. 5 is a graph illustrating a comparison of a groove depth of a emitting line formed on the steel plate according to the present exemplary embodiment with the related art.

In FIG. 5, Comparative Example shows a groove depth for a structure in which a laser beam is emitted without changing the tilt of the steel plate supporting roll like the related art, and Example shows a groove depth for a structure of changing the tilt of the steel plate supporting roll when the optical system is rotated.

As illustrated in FIG. 5, in the case of Comparative Example, it can be seen that the change amount in the groove depth along the steel plate width direction is large and the groove depth is not entirely uniform. On the contrary, in the case of Example, it can be seen that the groove depth is entirely formed uniformly in the width direction of the steel plate.

As described above, in the case of Example, the focal distance of the laser beam emitted onto the surface of the steel plate is constantly maintained along the emitting line, thereby minimizing a depth deviation of the lateral grooves on the surface of the steel plate.

In the laser beam emitting process, while the steel plate is molten by the laser beam, a large amount of fumes and molten iron spatters are generated. The fumes and the spatters contaminate the optical system, and if the molten iron remains in the groove, it is difficult to form a precise groove and the iron loss is not improved, and as a result, the product quality is deteriorated. Thus, the compressed dry air is sprayed into the grooves of the steel plate to remove the molten iron remaining in the grooves, and the fumes and the molten iron are directly sucked through the dust collecting hood to be removed. Therefore, it is possible to prevent the fumes from flowing into the optical system in the process of miniaturizing the steel plate magnetic domains, and to enhance the magnetic domain miniaturization efficiency by rapidly removing the fumes and spatters. Further, it is possible to further prevent the scattered light and heat of the laser beam from flowing into the optical system of the laser emitting equipment during the laser beam emitting process.

The grooves are formed on the surface of the steel plate through the laser beam emitting, and the steel plate subjected to the magnetic domain miniaturization is continuously moved and discharged to the outside through the outlet of the laser room.

The steel plate discharged from the laser room is subjected t a process of removing the hill-up and the spatters attached to the surface of the steel plate through the post-treatment process.

The steel plate is first in close contact with the steel plate while passing through the brush roll disposed outside the laser room to primarily remove the hill up and the spatters by the brush roll rotating at a high speed.

While the steel plate passing through the brush roll secondarily passes through the cleaning unit, the remaining hill up and spatters are finally removed through the electrolysis reaction between the steel plate and the alkali solution. The steel plate in which the hill up and spatters are removed while passing through the cleaning unit is conveyed to the post-treatment.

TABLE 1 Iron loss improvement rate (%) After laser emitting After heat treatment 9.5 11.6 9.7 12.9 11.5 13.5 8.4 11.6 8.6 11.8 8.5 11.7

Table 1 above shows an iron loss improvement rate of the directional electric steel plate by grooves formed on the surface of the steel plate with a thickness of 0.27 mm by the continuous wave laser beam emitting according to Example. As illustrated in Table 1, in the case of the steel plate subjected to the magnetic domain miniaturization by the Example, it can be seen that the iron loss is improved both after laser emitting and after the magnetic domains miniaturization with the laser beam and heat treatment.

While the exemplary embodiments of the present invention have been shown and described above, various modifications and other exemplary embodiments may be made by those skilled in the art. All of such modifications and other exemplary embodiments will be considered and included in the appended claims so as not to depart from the true spirit and scope of the present invention.

DESCRIPTION OF SYMBOLS

-   -   1: Steel plate     -   2A,2B: Steering roll (SR)     -   3: Steel plate center position control system     -   4: Warp measurement sensor     -   5A,5B: Tension bridle roll     -   6: Steel plate tension control system     -   7: Steel plate tension measuring sensor     -   8A: Deflector roll     -   8B: Deflector roll     -   8C: Intermediate deflector roll     -   9: Steel plate supporting roll     -   10: Brightness measurement sensor     -   11: Distance measurement sensor     -   12: Steel plate supporting roll position control system     -   13: Laser oscillator controller     -   14: Laser oscillator     -   15: Optical system     -   16: Laser beam     -   17: Air knife     -   18: Shielding unit     -   19A,19B,19C: Dust collecting hood     -   20: Laser room     -   21: Shower booth     -   22A,22B,22C,22D: Air curtain     -   23: Positive pressure device     -   24: Optical system lower frame     -   25: Constant temperature and humidity controller     -   26A,26B: Brush roll     -   27: Motor current control system     -   28: Brush position control system     -   29: Cleaning unit     -   30: Filtering unit     -   31: Emitting line     -   43,44: Elevating cylinder     -   45: Controller     -   46: Optical system angle calculating unit     -   47: Tilt calculating unit     -   48: Roll controller     -   49: Input unit 

The invention claimed is:
 1. A method for miniaturizing magnetic domains of a directional electric steel plate comprising: a steel plate supporting roll position adjusting step that controls a vertical direction position of a steel plate while supporting the steel plate progressing along a production line; and a laser emitting step that melts the steel plate by emitting a laser beam to form grooves on a surface of the steel plate for miniaturizing magnetic domains of the steel plate, wherein the laser emitting step comprises an angle changing step that changes an emitting line angle of the laser beam with respect to a width direction of the steel plate while an optical system emitting the laser beam onto the steel plate is rotated by a driving unit with respect to the steel plate, and a focal distance maintaining step that changes a tilt of the steel plate supporting roll which supports the steel plate according to a change in focal distance of the laser beam in the width direction of the steel plate, wherein the focal distance maintaining step comprises a tilt angle calculating step that calculates a tilt of the steel plate supporting roll in accordance with a change in focal distance of the laser beam on the surface of the steel plate due to a rotation of the optical system in the angle changing step, and a tilt adjusting step that changes the tilt of the steel plate supporting roll by moving each end of the steel plate supporting roll up and down, respectively, according to a value calculated in the tilt angle calculating step.
 2. The method of claim 1, wherein: in the angle changing step, the emitting line angle of the laser beam with respect to the width direction of the steel plate is changed to a range of ±4°.
 3. The method of claim 1, wherein: in the laser emitting step, with respect to the surface of the steel plate progressing in contact with the surface of the steel plate supporting roll in the form of an arc, by setting as a reference point an emitting position of the laser beam when the emitting direction of the laser beam passes through a central axis of the steel plate supporting roll, the laser beam is emitted to a position separated at an angle along an outer peripheral surface from the center of the steel plate supporting roll at the reference point.
 4. The method of claim 3, wherein: in the laser emitting step, the laser beam is emitted in a range of 3 to 7° separated from the center of the steel plate supporting roll along the outer peripheral surface thereof with respect to the reference point.
 5. The method of claim 1, wherein: the tilt angle calculation step includes an optical system angle calculating step of calculating a rotation angle of the optical system in accordance with the angle of the laser beam emitting line, a tilt calculating step of calculating a tilt angle of the steel plate supporting roll in accordance with the rotation angle of the optical system calculated by the optical system angle calculating step, and a roll controlling step of calculating a stretch driving amount of each of the elevating cylinders disposed at both ends of the steel plate supporting roll in accordance with the tilt value calculated in the tilt calculating step and applying an output signal to each of the elevating cylinders.
 6. The method of claim 5, wherein: in the optical system angle calculating step, the rotation angle of the rotated optical system is calculated in accordance with the interval of the laser beam and the angle of the emitting line from the moving speed of the steel plate.
 7. The method of claim 5, further comprising: a setting maintaining step of setting and maintaining an internal operating environment of a laser room in which the laser emitting is performed, wherein the setting maintaining step includes steps of isolating the inside of the laser room from the outside to block the inflow of external contaminants, and controlling an internal temperature, pressure, and humidity of the laser room.
 8. The method of claim 5, further comprising: a tension control step of applying tension to the steel plate so as to keep the steel plate in a flatly unfolded state.
 9. A device for miniaturizing magnetic domains of a directional electric steel plate comprising: a steel plate supporting roll position adjusting equipment that controls a vertical direction position of a steel plate while supporting the steel plate moving along a production line; and a laser emitting equipment that melts the steel plate by emitting a laser beam to form grooves on a surface of the steel plate, wherein the laser emitting equipment has a driving unit that changes an angle of the emitting line of the laser beam with respect to the width direction of the steel plate by rotating an optical system with respect to the steel plate, the optical system emitting the laser beam to the steel plate being rotatable by the driving unit, and further includes a focal distance maintaining unit which changes the tilt of the steel plate supporting roll supporting the steel plate according to a change in focal distance of the laser beam resulting from the driving unit changing the angle of the emitting line of the laser beam along the width direction of the steel plate.
 10. The device of claim 9, wherein: the laser emitting equipment emits the laser beam to a position separated at a angle along an outer peripheral surface from the center of the steel plate supporting roll at a reference point, by setting as the reference point an emitting position of the laser beam when the emitting direction of the laser beam passes through a central axis of the steel plate supporting roll, with respect to the surface of the steel plate progressing in contact with the surface of the steel plate supporting roll in the form of an arc.
 11. The device of claim 10, wherein: the laser emitting equipment emits the laser beam in a range of 3 to 7° separated from the center of the steel plate supporting roll along the outer peripheral surface thereof with respect to the reference point.
 12. The device of claim 10, further comprising: a laser room of accommodating the steel plate supporting roll position adjusting equipment and the laser emitting equipment separately from the outside and providing an operating environment for emitting the laser.
 13. The device of claim 12, wherein: the laser room accommodates the laser emitting equipment and the steel plate supporting roll position adjusting equipment to form an internal space to separate the equipments from the outside and has an inlet and an outlet formed at both sides in a progressing direction of the steel plate, and includes a positive pressure device for raising the internal pressure of the laser room therein, an optical system lower frame separating an upper space in which the optical system of the laser emitting equipment is positioned from a lower space through which the steel plate passes, and a constant temperature and humidity controller for controlling the internal temperature and humidity of the laser room.
 14. The device of claim 9, wherein: the focal distance maintaining unit includes a controller for calculating the tilt of the steel plate supporting roll in accordance with the change in focal distance of the laser beam on the surface of the steel plate due to the rotation of the optical system and controlling the tilt of the steel plate supporting roll, and elevating cylinders and which are provided at both ends of the steel plate supporting roll, respectively, and driven in accordance with a signal of the controller to lift and lower vertically the both ends of the steel plate supporting roll to change the tilt.
 15. The device of claim 14, wherein: the controller includes an optical system angle calculating unit for calculating a rotation angle of the optical system in accordance with the angle of the laser beam emitting line, a tilt angle calculating unit for calculating a tilt angle of the steel plate supporting roll in accordance with the rotation angle of the optical system calculated by the optical system angle calculating unit, and a roll controller for calculating a stretch driving amount of each of the elevating cylinders and disposed at the both ends of the steel plate supporting roll in accordance with the tilt value calculated by the tilt calculating unit and applying an output signal to each of the elevating cylinders.
 16. The device of claim 15, wherein: the controller further includes an input unit for inputting a laser beam emitting interval, a steel plate moving speed, and an angle of the emitting line.
 17. The device of claim 15, wherein: the optical system angle calculating unit calculates a rotation angle of the optical system rotated in accordance with the angle of the emitting line from the emitting interval of the laser beam and the moving speed of the steel plate.
 18. The device of claim 14, further comprising: a tension control equipment for applying tension to the steel plate so as to keep the steel plate in a flatly unfolded state.
 19. The device of claim 14, further comprising: a warp control equipment for moving the steel plate along the center of the production line without biasing the left and the right. 